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Sediment Distribution, McMurray Formation, Syncrude Oil-Sand Leases, Alberta, Canada

Adel O. Tammam, Gordon Stewart, George MacCallum

This study investigates the Lower Cretaceous McMurray Formation depositional units, and their vertical and lateral distribution within Syncrude oil-sand leases.

The McMurray Formation sediments are interpreted to be a product of a fluvially dominated depositional environment, which has gradually evolved into an estuarine and marine shoreface, consequent to a persistent marine transgression.

The lowermost sediments were deposited unconformably on an eroded argillaceous limestone surface of Devonian age. These early sediments appear to infill pre-Cretaceous drainage systems.

The patterns of these early drainage systems have been a controlling factor in the marine flooding and the distribution of the clastic sediments in the area. This is reflected in the concentration of predominantly sandy sedimentary bodies along the principal trend of the pre-Cretaceous lows, surrounded outward by increasingly clayey sedimentary bodies.

The lowermost sedimentary bodies trend east-west. A gradual change to a north-south trend is apparent upward in the stratigraphic column. This apparent change in depositional trends is related to the persistent marine transgression and the gradual marine flooding of the area, where the early drainage systems have gradually evolved into larger estuaries with larger inlets. Within these large inlets, and eventually throughout the area, the persistent marine flooding has distributed the sediments in linear and shoal-like sedimentary bodies, parallel with the local front of the marine transgression.

The knowledge of such a controlled sediment distribution has a major implication in exploration and mining activities, as well as in formulating a depositional model applicable throughout the Athabasca region.

AAPG Search and Discovery Article #91043©1986 AAPG Annual Convention, Atlanta, Georgia, June 15-18, 1986.